It all depends on the contractual agreements signed by the union and the individual airline. I would venture to say that while on RESERVE you will probably get 10- 12 days off a month on average. Once you are able to hold a line based on your seniority it may increase further depending on what your seniority can hold. I was able to get some months with 16-17 days off. Your quality of life while on RSV will be better if you live where you are based. In the States many people simply commute to work but that puts an added strain especially when on RSV. If you are on RSV and you are able to determine your potential "call up number" you can very easily have a somewhat normal day and not have to sit at home waiting for the phone to ring. Just get ready, keep your stuff in your car and be ready to report within an hour or two, depending on call up rules for your airline. I have spent many a RSV day on the golf course and elsewhere....
As far as lifestyle etc--you get salary,perdiem, days off, travel benefits (standby) and some will offer a retirement. Trips can be day trips, 2/3/4 day trips. Some cargo haulers (ACMI) have on for call for set number of days as flying is unpredictable. As you are coming from an A6 operator you will find that there will be no housing, utility, education allowance.i You will drive yourself to work!!
I suggest you look at
Home | AirlinePilotCentral.com for profiles of different airlines, pay etc as well as projected time to command. Do not apply to any airline until you have the green card in your hand. One of the questions asked on the application is "Do you have the legal right to work in the US." If you fill out an app prematurely and answer YES, you risk getting a call and they will reject and blacklist you if you don't have the green card.
And by the way, don't be surprised or offended if you are asked often "where is Sri Lanka?"! My wife was once on a flight from DXB to ATL and the immigration officer asked her if she was carrying spices and goods from India(he was convinced Dubai was in India). So my wife (a U.S. school teacher) gave him a quick lesson in geography.